This invention relates to a system for monitoring fluids for microbial contamination and, more particularly, to such system designed to automatically sample potentially contaminatable fluid and indicate when contamination of such fluid occurs.
The invention is particularly useful for detecting contamination of urine in catheterized patients, who are susceptible to infection of the urinary tract resulting in contamination of the urine. Prior to the present invention, contamination of urine in catheterized patients was monitored by periodically collecting individual urine samples and culturing each sample to determine the presence of contamination. Because each urine sample had to be sent to a laboratory to be individually cultured and because of the expense of collecting and processing frequent individual cultures resulting in an average time delay before the collection of the first sample of urine after contamination appears in the urine, a substantial amount of time would normally elapse between the time of contamination appearing in the urine and the time of determining that the urine was contaminated. As a result, by the time it had been determined that the urine was contaminated, the patient often already had a massive infection. Moreover, each separate sample collection was subject to accidental contamination, leading to occasional false positive cultures.
The present invention overcomes these problems of the prior art technique by providing a much earlier indication of the presence of contamination. This is achieved by providing at the site of a patient a liquid culture medium and periodic urine samples are automatically fed into the same tracer-labeled culture medium over an extended time interval. The cost of using the system does not vary with the number of samples collected and, accordingly, the frequency of sampling is based solely upon medical requirements, without regard to the cost of the additional samples. As soon as contamination of the urine begins, the first sample containing contamination will be aseptically collected and incubation will begin instantaneously in the growth medium. As a result, the growth medium will evolve gas, which will be detected by a detector to provide an early indication of the presence of such gas thus indicating the presence of microbial contamination in the urine. The system differs from the prior art systems, not only in the automatic sampling of the urine from the patient, but also in the fact that each urine sample is aseptically diverted into the same culture medium as the previous samples. Each urine sample can be fed into the same culture medium because the system is designed only to detect the presence of contamination and the samples of urine taken from the patient prior to infection of the patient would be sterile and would not effect the ability of the culture medium to respond to a later contaminated sample.
It will be evident that the system as described is also applicable to detect the presence of contamination in other fluids by automatically taking periodic samples of the fluids including fluids from wound drainage, dialysis fluids, peritoneal cavity drainage, cerebro-spinal fluid drainage, exhaled air, fluids undergoing or intended for intravenous administration or inhalation, fluids in industrial processes including food preparations, particles of solids or liquids within fluid streams, or any normally sterile or culturable fluid. It likewise will be evident that any convenient means of detecting microbial growth may be used in the system.